Truck will not start I know it is getting gas

The easiest way to check for sparks for just a single person is to simply get some starting fluid and spray it directly into the throttle body. Then you put the air cleaner back on and turn the key. If the engine starts for a second or so and then shuts off, you have sparks.

A better way (a little harder to do by yourself, but maybe still doable) is to get a $10.00 spark tester from the store and check each cylinder individually. Here is a link to the one that I have: https://www.amazon.com/Lisle-20610-Inline-Spark-Tester/dp/B0002STSC6/ref=sr_1_3?ie=UTF8&qid=1500950215&sr=8-3&keywords=spark+tester

It has worked well for a few years now, even on my lawn mower.

The other way, more complex and almost definitely needing a helper, is the following:

https://www.2carpros.com/articles/how-to-test-an-ignition-system.

The other thing to consider is that just because you have fuel getting to the rail does not mean that it has enough pressure. Nor does it mean that the injectors are pulsing. Having some experience with Chevrolet trucks, I am inclined to think that your fuel pump might be weak, but still pumping. Just like the last two that I have replaced. So if you do see that there are good sparks, the next thing to do is to get a fuel pressure tester (can be borrowed from AutoZone with a deposit) and see what you get.

Let us know what you find.

Please let us know what happens.

Cheers, Ken